The discussion below is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.
Aspects of the invention relate to generating auxiliary power for a wind turbine and, in particular, though not exclusively, to a method for generating auxiliary power for a wind turbine, a wind turbine comprising an auxiliary power supply, a controller and a converter for use in such wind turbine and a computer program product using such method.
Wind turbine technology and in particular offshore wind turbine technology is a rapidly developing field of technology. At offshore locations higher wind speeds are available and installation of larger size wind turbines are possible when compared with the onshore systems. The installation and operations of such wind parks provide some technological challenges. The wind turbines are floating or installed on a submarine foundation and are electrically interconnected with submarine power cables. Moreover, such wind parks are typically installed in relatively remote areas, hence the control system of the wind farm and/or the control system in each wind turbine of the wind farm should be able to take measure when problems occur during operation. In such circumstances, the wind turbines in a wind park should be configured to autonomously deal with problems arising during the operation of the wind turbine.
One of the problems is that a wind farm or part of the wind turbines of the wind farm may become disconnected from the electrical grid, e.g. because of planned switching action, protective switching of a circuit breaker in the grid or protective switching of a circuit breaker because of an internal wind turbine failure such as a (partial) failure of the (main) converter.
After detection of a such failure circuit breakers may automatically disconnect a turbine from the grid and sets itself to a parking or standby state by stopping rotation of the blades and by pitching the blades in the vane position. Such standby state will last until the disconnected wind turbines can be reconnected to the grid. During the standby state, the wind turbine controller and other turbine components, e.g. the environmental controller, which controls the environmental parameters (temperature, humidity, etc.) of the wind turbine installation to stay within the requested limits, have to be supplied with power from an auxiliary power source, since the power from the grid is not available.
Moreover, there are also other situations possible, e.g. an internal failure of some elements in the wind turbine, wherein a turbine is not physically disconnected from the grid but still requires power from an auxiliary power supply.
A conventional wind turbine typically uses an uninterruptible power supply (comprising e.g. a battery system, super capacitors, a diesel generator set or combinations thereof) as the auxiliary power source. Diesel generators however require maintenance and refueling and are thus less suitable for use in offshore and/or remote wind farm systems. Moreover, batteries are sensitive to temperature changes and—in order to ensure a power supply over a long duration—typically a large number of batteries is required. Moreover, over time the capacity of the batteries may degrade.
From the above it follows that in order for a wind turbine to autonomously deal with problems arising during the operation a reliable auxiliary power source is required which is capable of delivering power to a wind turbine for a relatively long period of time. Hence, there is a need in the prior art for methods and systems for improved ways of generating auxiliary power for use in a wind turbine.